Edwin t



(No Model) B. T. GREE'NFIELD. TBLEPHONIG TRANSMITTING INSITITRUMEN'I.

-. No. 244,590. Patented July 19,1881,

7 Q} i k 1* 4 WI g 1% N4 P ETERS PholvLithugmpher. Wahlngmn, ac

UNITED S AT PATENT OFFICE..

' EDWIN T. GREENFIELD, OFBROOKLYN, ASSIGNOR rerun HOLMES BURG- LAR ALARM TELEGRAPH COMPANY, on NEW YORK CITY, N. Y.

- brations for the transmission of spoken mes '10 tab a TELEPHQNIC TRAN SlVllTT lNG-l NST RUMEN T.

' SPECIFICATION forming partof 'Letters Patent No. 244,5 90, dated July 19, 1881.

- Application filed m, 1880. (No n1odel.)' i

To all whom it may concern:

Be it known that I, EDWIN T. GREENFIELD, of the city of Brooklyn, in the State of New York, have invented a new and. useful Improvement in TelephonicTransmitting-Instruments, of which the followingis a specification.

' The present invention relates to the instrumentality by means of which undulatory visages or other audible sounds are produced in telephonic conductors, and the objectis to" provide an apparatus with which asingle' op-. erator placed. at a central station can send a message simultaneously over a multiplicity of lines diverging from such station.

The invention consists, in general, in combining in asingle transmitting-instrument two or" more induction-coils, or two or more'battery-wires, such battery-wires, or the secondary wires of such induction-coils, communicating with the different customers in the system.

The invention is fully illustrated in the accompanying drawings, in which Figure 1 is a perspective view of the invention, representing a multiple transmitter adapted for use with four separate line-wires, each connecting with a single customer. The cover of the instrument, carrying the mouth-piece, the diaphragm, and the connected parts, is shown as opened, and a portion of the case as broken away, in order better to exhibit the internal construction. Fig. 2 is a sectional view of the mouthpiece, the diaphragm, and the connected parts. Fig. 3 represents ga modified construction, in which primary currents are used for the transmission of the messages.

The construction, arrangement, and operation of the parts shown in Fig. 2 are substan-- tially the same as those already existing in the well-known Edison transmitter, and therefore do not here require any detailed description. The present invention, moreover,does not depend upon the special constructionof these parts, as these parts of the Edison transmitter may readilybe replaced by the corresponding parts of other well -known and practical instruments. e

Referring to Fig.1 more in detail, A, B, O,- and D represent four induction-coils, the pri- 5o inary wiresa, b, c, and d of which are each connected with the same battery-wire E, and the secondary wires a b c d of which lead off in separate directions to the respective recei'vin g instruments of different customers. These several induction coils are sorgrouped as to be all brought under the influence of a common mouth-piece and diaphragm, orwhatever other instrumentality may be used for exciting in them the und ulatory vibrations of the elec'tiiccurrent necessary to the transmission of telephonic messages.

Under the construction here shown it results that whenever the diaphragm of the instrument is put into vibration corresponding un- 6 5 dulations or fluctuations are produced in the primary current passing'over the battery-wire E, and this in turn generates corresponding I undulations in the secondary wire of each of the coils to which the corresponding line-wire is connected, and thus a message or sound spoken or otherwise delivered into the common mouth-piece or against the common diaphragm will be transmitted along each of the line-wires to the receiving-instrument at its farther end. It will be readily understood that in order thus to send amessage over several wires simultaneously a stronger batterycurrent .is required than would serve for a single line. 7

The principle involved-in the above con-- struction is applicable likewise tothe use of a battery-current instead of an induced current as the medium for transmitting the message. Such adaptation is illustrated in Fig. 3, in '8 5 which the battery-wire on leaving the transmitter proper,- branches into as many different lines as there are customerstobe served. Under this construction, also, any undulations produced in the electric current upon the main 0 wire will be perpetuated over each of the branches, and thus a single operator properly connected with the several customers represented by these branch lines will be enabled to send the same message tothem all simul- 5 V 7 taneously, as shown in Fig. The different lines should branch from a central point, substantially at the transmitter, in which respect, both as regards the construction itself and the effect produced, the present invention will be found to differ from the use of branch wires leading off at various and widely-separated points along a main telephonic wire.

The uses of this multiple transmitter are various. Obviously its chief use will be where it is desired to transmit the same message simultaneously to several difl'erent points, in which case it will, of course, be necessary to have the operators in the several receivingstations in readiness at the same time, which can be effected by any prearranged system of signals. This compound transmitter will also be found of utility in the improved system efi'ecting telephonic exchanges, which forms the subject of an application for Letters Patent filed by me contemporaneously herewith, in which it is proposed to use it in connection with a multiple receiver, also connected with the same lines in such a manner that a single listener can receive any orders transmitted over any one of the many lines that converge to such receiver. Vhen this transmitter is thus used any customer putting his telephone into circuit with his line will be able to hear any orders that the listener-on at the .central station may be repeating to the switchman, and accordingly will withhold his own order until by the cessation of sounds he ascertains that the listener-on is for the moment disengaged; and thus all danger of confusion from the interference of orders sent in 3 5 to the central station will be avoided.

Referring, again, to Figs. 1 and 3, it will be apparent that the invention need not be limited in practice to the use of the exact number of coils or branch wires there shown. It 40 will be found, in practical operation, that the number can be very largely increased to correspond to the number of customers joined in a single system.

What is claimed as new is-- 1. The combination, in a single telephonic transmitter, of two or more induction coils, each connected with its own' independent linewire, substantially as and for the purpose set forth.

2. In combination with a telephonic transmitter operated by a battery-current, two or more line-wires branching from such instrument, substantially as and for the purpose set forth.

3. The combination of two or more line-wires with a single telephonic transmitter by means of induction-coils arranged with reference to a common diaphragm, so as to be controlled simultaneously thereby, substantially as and 60 for the purpose set forth.

EDWIN T. GREENFIELD.

Witnesses:

H. F. NEWBURG, J As. TONMEY. 

